1. Field of the Invention
This invention relates to a battery with a separate electrolyte storage tank, particularly a tank which can discharge the electrolyte to a battery without employing a mechanical expulsion system.
2. Prior Art
Batteries required to be dormant for extended periods of time (up to one or more years) prior to operation are suitably designed with an electrolyte reservoir or tank separate from the battery cell or cells. The battery is then activated by expelling the electrolyte from the tank into the cell or cells. Positive expulsion systems employing gas-driven pistons or bellows, may be costly, unreliable or both. An electrolyte management system for such tank, that is uncomplex and reliable is needed.
There has now been discovered such a system which employs a surface tension electrolyte tank which (1) allows electrolyte to be expelled by a pressurizing gas from such tank; (2) excludes the pressurizing gas from the battery cell and (3) retains the electrolyte in the battery cell under adverse acceleration fields. That is, as described below, the invention employs a liquid-coated barrier screen which permits the passage of electrolyte therethrough while blocking or containing such gas.
The prior art describes the use of porous liquid surface tension gas barriers in batteries. Thus U.S. Pat. No. 4,565,749 to van Ommering et.al. (1986) discloses a bipolar metal-gas battery cell stack in which a hydrophobic barrier is utilized to prevent intercell migration of electrolyte and secondary gases U.S. Pat. No. 4,543,303 to Dantowitz et.al. (1985) discloses batteries containing a plurality of electrochemical fuel cells in which the cathode side outlet of each cell includes cell water/gas separator elements which remove the product water from the outlet gas stream. Each separator includes a hydrophilic, porous matrix, which when wetted will permit the flow of liquid but not the passage of gas therethrough below a certain critical pressure level, normally identified as the "bubble pressure", which is related to pore size and surface tension of the liquid imbibed in the porous hydrophilic membrane.
U.S. Pat. No. 4,514,474 Momyer et.al. (1985) describes an air cathode structure for use in primary batteries. The structure includes a porous separator which is wetted with electrolyte and maintains a high bubble pressure to effectively preclude air from percolating through the separator into the electrolyte.
None of the above references suggest the use of such surface tension gas barrier for separate electrolyte storage and subsequent gas discharge of electrolyte therethrough into the battery cell while excluding the pressurizing gas from such battery cell.